Portable Solar Versatility

The essence of survival is preparedness. The essence of surviving comfortably is preparing ingeniously.

This Instructable follows my creation of a multi-use solar apparatus, built around an up-cycled Fresnel lens. It is multi-use in that one can use it to distill potable water, sterilize surgical instruments, cook food, and as an ignition source (as-is); with further accessorization and creation, the heat and/or steam generated could be harnessed to create electrical energy in multiple ways, and could also be used for heating in a broader sense than for fire, food, and water (I wouldn't mind surviving with the occasional hot shower or dip in the hot tub ;-) ).

More seriously though, this could save my life at some point. Farther from home, consider the tens of thousands who still die from cholera each year- in most cases all, literally all, that is needed to overcome cholera is clean water. Being light-weight, inexpensive, and man-portable, this sort of arrangement could be put to use where the infrastructure doesn't exist to do what this thing does.

I hope this build incites some ingenuity within your own mind to come up with something worth sharing! Enjoy!

As I built it the following tools and materials were used (but if you dont have the time or resources you can improvise; just find yourself the right TV to harvest the lens from):

MIG welder (wire welder with CO2)

Plasma cutter

Drill press

Hand drill

Step bit

Drill bit set

Automatic center punch

File (flat mill bastard, 3/4')

Vise (for bending round bar)

5/16'' Nuts, bolts, washers, and wing nuts

3/4'' & 1'' square tube steel

1/4'' round steel bar

Fresnel lens from broken TV

Over the winter, my old (ca. 1990's) Mitsubushi rear projection TV went dead. Naturally (for me, anyway), I took it apart before discarding to salvage anything that could be of use to me in the future. Those TV's are surprisingly packed with useful components that can easily be removed and recycled into electronics projects. Anyway, this is how I came across the Fresnel lens which is the main component of the screen. It was already in a nice aluminum frame, so I kept the screen intact in the frame and put it in my garage because I had a feeling I could do something good with it...

There is a film on the screen which functions to provide pixellation, to put it simply. It was attached with an adhesive which luckily stayed on the film and came cleanly off the lens. The film is on the outside (smooth); take care not to damage the inside surface of the lens, which is more or less comprised of a great many ridges arranged radially from the center. These ridges are what allow the lens to be useful to us and they are fragile, so try not to mess them up or get them dirty.

I knew that I wanted the entire apparatus to store flat so as to take up little space (if I'm keeping it around for a true survival situation, it shouldn't take up much space or be inconvenient to have around, or it will eventually be at risk of leaving my possession. My wife is a prepper but she doesn't like junk laying around).

To that end, I did some preliminary sketching and came up with a rudimentary design which makes use of some square tube steel I had laying around. I like to do my design on paper with as much detail as the real thing will have-- and doing so pays dividends as I discover problems when I can erase them and solve with a pencil rather than grinding welds and refabricating pieces of steel.

Here are pics of the process of building the frame. I first built the base, so that I could make use of as much of the space as possible between the bottom of the lens frame and the steel base. After getting that built to my satisfaction, I added the arms which the lens frame actually mounts to, which in turn mate with the base and secure with the hitch pins you can see in the picture. I'm not going into a great level of detail about my fabrication process because I'd encourage you to re- or up-cycle whatever materials you have laying around, and also if you have the tools I mentioned at the beginning then you probably don't need me to tell you how to do it. Also, I polish the rust off of my steel stock before using to make it easier to paint.

Safety note- I have to assume that you know what you're doing if you have these tools to use. At least protect your eyes! If you don't you can take this as an opportunity to practice your dolphin noises ('cuz you'll have to learn to echolocate when you lose your eyes. I bet you'd really annoy dolphins. Hardy har har.) Also if you use a file make sure it has a handle so you don't skewer yourself.

Now that we have a useful frame to build from and our lens is safe and ready for some sun, I decided to build a steel vessel for the purpose of distilling dirty water into potable water. I used 16 guage mild steel; if you're improvising you can use just about any metal container that will let you form a seal to the cooling coil and which can handle the heat you'll be putting into it.

Not my best cutting/welding work, but after all its a prototype and it is waterproof.

I had this copper coil laying around from a project I did in which I used a mini-fridge to keep my minnows cool during the hot summer fishing months. It's half-inch soft copper, like is commonly used for gas or refrigeration lines. The fittings were already on there so I left them; they aren't really necessary because the clear flexible tubing is a snug fit over the pipe. As you can see I used some of the clear tubing between the water box and the cooling coil, so as to avoid unnecessary heat transfer from the water box to the cooling coil, and also to provide a view of the steam being generated.

Now that I have the water box and cooling coil portions of the still done, I needed to mount the water box near the focal point of the lens. In previous tests (using the lens to ignite paper and pizza boxes) I determined the focal length of this particular lens to be 31" plus or minus about half an inch. Again using materials I had on hand, I chose to use some 1/4' round steel bar. I drilled holes in the lens frame to accomodate the steel bar, and cut and bent it so that when completed the surface of the water box was at 29 1/2' from the lens. It doesn't have to be right at the focal length, because the energy is still hitting the same surface and so isn't less efficient. At this distance I get a 3/4'' dot of focused light.

Once the sun finally came out, it was just before 6 PM. I added a half liter of tap water and placed the apparatus in the sun, positioning to achieve optimal focus. After about 10 minutes steam became visible, and after another 10 the box was too hot to touch.

I calculated the are of my lens to be 0.76 meters square. Online I found that the typical solar flux at my location is about 1,000 W/M2, so this should easily be able to harness 700+ Watts.

In the future, I'll try cooking with my small dutch oven, and also modify the water box to make it use the solar radiation more efficiently- first and foremost I'll paint it black and insulate the sides that don't need to be open.

Thanks for reading and feel free to email me with any questions or comments!

Also I'm entering this into the Outdoor Survival contest so please, if you feel that it's deserving, vote for this Instructable!